Re: [Intel-gfx] [PATCH 4/6] drm: scrambling support in drm layer

"Sharma, Shashank" <shashank.sharma@xxxxxxxxx> · Thu, 2 Feb 2017 11:25:39 +0530

Thanks for the review, Dhinakaran.


Regards

Shashank


On 2/2/2017 1:23 AM, Pandiyan, Dhinakaran wrote:
On Wed, 2017-02-01 at 18:14 +0530, Shashank Sharma wrote:
HDMI 2.0 spec mandates scrambling for modes with pixel clock higher
than 340Mhz. This patch adds few new functions in drm layer for
core drivers to enable/disable scrambling.

This patch adds:
- A function to detect scrambling support parsing HF-VSDB
- A function to check scrambling status runtime using SCDC read.
- Two functions to enable/disable scrambling using SCDC read/write.
- Few new bools to reflect scrambling support and status.

Signed-off-by: Shashank Sharma <shashank.sharma@xxxxxxxxx>
---
  drivers/gpu/drm/drm_edid.c  | 131 +++++++++++++++++++++++++++++++++++++++++++-
  include/drm/drm_connector.h |  24 ++++++++
  include/drm/drm_edid.h      |   6 +-
  3 files changed, 159 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 37902e5..f0d940a 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -37,6 +37,7 @@
  #include <drm/drm_edid.h>
  #include <drm/drm_encoder.h>
  #include <drm/drm_displayid.h>
+#include <drm/drm_scdc_helper.h>
  
  #define version_greater(edid, maj, min) \
  	(((edid)->version > (maj)) || \
@@ -3814,6 +3815,132 @@ static void drm_detect_hdmi_scdc(struct drm_connector *connector,
  	}
  }
  
+static void drm_detect_hdmi_scrambling(struct drm_connector *connector,
+				 const u8 *hf_vsdb)
+{
+	struct drm_display_info *display = &connector->display_info;
+	struct drm_hdmi_info *hdmi = &display->hdmi_info;
+
+	/*
+	 * All HDMI 2.0 monitors must support scrambling at rates > 340M.
+	 * And as per the spec, three factors confirm this:
+	 * * Availability of a HF-VSDB block in EDID (check)
+	 * * Non zero Max_TMDS_Char_Rate filed in HF-VSDB
+	 * * SCDC support available
+	 * Lets check it out.
+	 */
+
+	if (hf_vsdb[5]) {
+		display->max_tmds_clock = hf_vsdb[5] * 5000;
Comment explaining or quoting where the 5000 comes from?
Sure, can be done.

+		DRM_DEBUG_KMS("HF-VSDB: max TMDS clock %d kHz\n",
+			display->max_tmds_clock);
+
+		if (hdmi->scdc_supported) {
+			hdmi->scr_info.supported = true;
+
+			/* Few sinks support scrambling for cloks < 340M */
+			if ((hf_vsdb[6] & 0x8))
+				hdmi->scr_info.low_clocks = true;
+		}
+	}
+}
+
+/**
+ * drm_check_scrambling_status - what is status of scrambling?
+ * @adapter: i2c adapter for SCDC channel
+ *
+ * Read the scrambler status over SCDC channel, and check the
+ * scrambling status.
+ *
+ * Return: True if the scrambling is enabled, false otherwise.
+ */
+
+bool drm_check_scrambling_status(struct i2c_adapter *adapter)
+{
+	u8 status;
+
+	if (drm_scdc_readb(adapter, SCDC_SCRAMBLER_STATUS, &status) < 0) {
+		DRM_ERROR("Failed to read scrambling status\n");
+		return false;
+	}
+
+	status &= SCDC_SCRAMBLING_STATUS;
+	return status != 0;
+}
+
+/**
+ * drm_enable_scrambling - enable scrambling
+ * @connector: target drm_connector
+ * @adapter: i2c adapter for SCDC channel
+ * @force: enable scrambling, even if its already enabled
+ *
+ * Write the TMDS config over SCDC channel, and enable scrambling
+ * Return: True if scrambling is successfully enabled, false otherwise.
+ */
+
+bool drm_enable_scrambling(struct drm_connector *connector,
+					struct i2c_adapter *adapter, bool force)
+{
+	u8 config;
+	struct drm_hdmi_info *hdmi_info = &connector->display_info.hdmi_info;
+
+	if (hdmi_info->scr_info.status && !force) {
+		DRM_DEBUG_KMS("Scrambling already enabled\n");
+		return true;
+	}
+
+	if (drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config) < 0) {
+		DRM_ERROR("Failed to read tmds config\n");
+		return false;
+	}
+
+	config |= SCDC_SCRAMBLING_ENABLE;
+
+	if (drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config) < 0) {
+		DRM_ERROR("Failed to enable scrambling, write error\n");
+		return false;
+	}
+
+	hdmi_info->scr_info.status = drm_check_scrambling_status(adapter);
+	return hdmi_info->scr_info.status;
+}
+
+/**
+ * drm_disable_scrambling - disable scrambling
+ * @connector: target drm_connector
+ * @adapter: i2c adapter for SCDC channel
+ * @force: disable scrambling, even if its already disabled
+ *
+ * Write the TMDS config over SCDC channel, and disable scrambling
+ * Return: True if scrambling is successfully disabled, false otherwise.
+ */
+bool drm_disable_scrambling(struct drm_connector *connector,
+					struct i2c_adapter *adapter, bool force)
+{
+	u8 config;
+	struct drm_hdmi_info *hdmi_info = &connector->display_info.hdmi_info;
+
+	if (!hdmi_info->scr_info.status && !force) {
+		DRM_DEBUG_KMS("Scrambling already disabled\n");
+		return true;
+	}
+
+	if (drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config) < 0) {
+		DRM_ERROR("Failed to read tmds config\n");
+		return false;
+	}
+
+	config &= ~SCDC_SCRAMBLING_ENABLE;
+
+	if (drm_scdc_writeb(adapter, SCDC_TMDS_CONFIG, config) < 0) {
+		DRM_ERROR("Failed to enable scrambling, write error\n");
+		return false;
+	}
+
+	hdmi_info->scr_info.status = drm_check_scrambling_status(adapter);
+	return !hdmi_info->scr_info.status;
+}
+
  static void drm_parse_hdmi_deep_color_info(struct drm_connector *connector,
  					   const u8 *hdmi)
  {
@@ -3928,8 +4055,10 @@ static void drm_parse_cea_ext(struct drm_connector *connector,
  
  		if (cea_db_is_hdmi_vsdb(db))
  			drm_parse_hdmi_vsdb_video(connector, db);
-		if (cea_db_is_hdmi_forum_vsdb(db))
+		if (cea_db_is_hdmi_forum_vsdb(db)) {
  			drm_detect_hdmi_scdc(connector, db);
+			drm_detect_hdmi_scrambling(connector, db);
+		}
  	}
  }
  
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 2435598..b9735bd 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -90,6 +90,26 @@ enum subpixel_order {
  
  };
  
+
+/**
+ * struct scrambling: sink's scrambling support.
+ */
+struct scrambling {
+	/**
+	 * @supported: scrambling supported for rates > 340Mhz.
+	 */
+	bool supported;
+	/**
+	 * @low_clocks: scrambling supported for rates <= 340Mhz.
+	 */
+	bool low_clocks;
The naming for low and high clock rates looks asymmetric.
I dont get it, I dont have a high clock here, can you please elaborate ?

- Shashank
+	/**
+	 * @status: scrambling enabled/disabled ?
+	 */
+	bool status;
+};
+
+
  /**
   * struct drm_hdmi_info - runtime data about the connected sink
   *
@@ -108,6 +128,10 @@ struct drm_hdmi_info {
  	 * @scdc_rr: sink is capable of generating scdc read request.
  	 */
  	bool scdc_rr;
+	/**
+	 * scr_info: sink's scrambling support and capabilities.
+	 */
+	struct scrambling scr_info;
  };
  
  /**
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 43fb0ac..d24c974 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -462,5 +462,9 @@ void drm_edid_get_monitor_name(struct edid *edid, char *name,
  struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
  					   int hsize, int vsize, int fresh,
  					   bool rb);
-
+bool drm_enable_scrambling(struct drm_connector *connector,
+				struct i2c_adapter *adapter, bool force);
+bool drm_disable_scrambling(struct drm_connector *connector,
+				struct i2c_adapter *adapter, bool force);
+bool drm_check_scrambling_status(struct i2c_adapter *adapter);
  #endif /* __DRM_EDID_H__ */

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